//#include<iostream>
//using namespace std;
//#include<cmath>
//#define S(a,b,c) (a + b + c)/2
//#define AREA(a, b, c) sqrt(S(a, b, c)* (S(a,b,c)-a)*(S(a, b, c)-b)*(S( a,b , c)-c))
//int main()
//{
//	float a, b, c;
//	cout << "input a, b, c:";
//	cin >> a >> b >> c;
//	if (a + b > c && b + c > a && a + c > b)
//		cout << "area=" << AREA(a, b, c) << endl;
//	else
//		cout << " no" << endl;
//	return 0;
//}
//#include<iostream>
//#include<cmath>
//using namespace std;
//
//#define S(a, b, c) (a + b+ c)/2
//
//#define AREA(a,b ,c , d) sqrt(d*(d - a)*(d - b)*(d - c))
//int main()
//{
//	float a, c, b;
//	cout << "input a, b, c: " << endl;
//	cin >> a >> b >> c;
//	if (a + b > c && a + c > b && b + c > a)
//	{
//	    float s = S(a, b, c);
//
//		cout << "area= " << AREA(a, b, c, s);
//	}
//	else
//		cout << " no!" << endl;
//}